Trimming Overwintering Leggy Annuals
Long leggy stems can be cut down to size. Use a handpruner or garden scissors for the job. Cut overgrown stems back, just above a set of healthy leaves or node, the place where leaves were once attached. You can cut back all the stems or stagger this over a few weeks, leaving some leaves in place to create energy for the plant.
Root some of the trimmings to increase the number of plants for your garden or to share with others. Cut the stems into 4 to 6 inch pieces with at least one set of leaves attached. Stick the cut end, with the lowest node buried, into moist vermiculite, perlite or a well-drained potting mix to root.
Place in a bright location out of direct light and keep the rooting mix moist. Loosely cover with an open plastic bag while the cuttings root.
A bit more information: Use a rooting hormone, available at most garden centers, for hard-to-root cuttings. These contain hormones to encourage root development. Dip the cut end into the material and place the cutting in vermiculite, perlite or a well-drained potting mix to root.